Add Simplified Chinese as a system language

The installer asks for the language before the keyboard, and
Setup > Language (omarchy language en|zh) switches it later. Under
zh_CN the menu reads its labels from omarchy-menu.zh-cn.jsonc, the
shell from I18nZh.js through I18n.tr, and notifications are worded
by their sender through omarchy-text, which reads the same table.
User text is never translated.

shell/Ui/ConfirmDialog.qml

@@ -7,8 +7,8 @@ Item {
 
   property bool opened: false
   property string message: ""
-  property string cancelText: "Cancel"
-  property string confirmText: "Confirm"
+  property string cancelText: I18n.tr("Cancel")
+  property string confirmText: I18n.tr("Confirm")
   property int selectedIndex: 1
   property color background: Commons.Color.background
   property color foreground: Commons.Color.foreground